/ Dictionary / Index C cosmic background radiation: Meaning and Definition of Find definitions for: cos'mic back'ground radia"tion Pronunciation: [key] — Astron. Astron. electromagnetic radiation coming from every direction in the universe, considered the remnant of the big bang and corresponding to the black-body radiation of 3 K, the temperature to which the universe has cooled. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. cosmic cosmic dust Related Content Daily Word Quiz: wary Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language